1. Field of the Invention
The present invention relates to improved wax compositions and fibrous substrates coated therewith, and more particularly to compositions of a fully refined paraffinic petroleum wax, a recrystallized heavy intermediate petroleum wax, a microcrystalline petroleum wax and polymeric hydrocarbon compounds. In addition, the wax compositions contain a tackifier resin and a phenolic anti-oxidant. These wax compositions are particularly suitable for coating fibrous substrates. The copending application of Richard L. Jones entitled, "Hot Melt Wax Coatings For Fibrous Substrates", Ser. No. 07/307,875, filed Feb. 6, 1989, describes fibrous substrates and a process for coating said substrates using the wax compositions disclosed herein, the disclosure of which is incorporated herein by reference.
It is known to coat fibrous substrates, for example, paper and the like with wax and wax like compositions. These coatings are particularly useful in preventing the migration of moisture either out of or into a container treated therewith. Numerous waxes have been used as coatings for fibrous substrates in the past, including animal and vegetable waxes, for example, bees wax, wool wax, cotton wax and the like.
The mineral waxes, in particular, the petroleum waxes such as paraffin wax, microcrystalline wax and the like are more commonly used at the present time to coat fibrous substrates. Blends of these waxes have additionally been used in the past. These wax coatings, however, generally exhibit one or more deficiencies, such as, lack of sufficient hardness, scuff resistance, tensile strength, resistance to cracking, an opaque color and other undesirable characteristics. In the absence of microcrystalline waxes, distillate paraffin waxes are usually too brittle to be effective as coating waxes, particularly at ambient temperatures such as room temperature and below. To overcome these and other difficulties it has become common practice to use blends of certain additives in wax compositions. The use of polymers as additives in waxes has greatly improved certain characteristics in wax coatings, however, many wax coatings which use these additives still suffer from one or more disadvantage such as an opaque color, poor resistance to moisture, as well as insufficient heat and thermal stability, grease resistance and gloss stability. The wax compositions herein overcome these difficulties and, in addition, when applied as a coating to fibrous substrates are substantially clear in color. This is important because it allows for writing and marks on the fibrous substrate to be visible to the eye after the coating is applied.
2 Description of the Prior Art
Wax compositions, paper products containing coatings of wax compositions and processes for making and producing the same are known and are currently practiced commercially.
For example, U.S. Pat. No. 3,175,986 issued Mar. 30, 1965 relates to paraffin wax-containing compositions suitable for coating and laminating paper board, carton board and the like. The wax compositions consist of a paraffin wax, an ethylene-vinyl acetate copolymer, a microcrystalline wax and a terpene resin.
U.S. Pat. No. 3,243,396 issued Mar. 29, 1966 discloses a plastic formulation suitable for coating paper, cardboard, etc. The plastic formulations consist of paraffin wax, microcrystalline wax, ceresin wax, a solid polyethylene resin, and an isotactic polyterpene.
U.S. Pat. No. 3,297,610 issued Jan. 10, 1967 relates to wax compositions which are described as especially useful as coatings for paper or other packaging materials. The wax composition consists of a blend of a paraffinic petroleum wax, an isoparaffinic petroleum wax, and two different microcrystalline petroleum waxes.
U.S. Pat. No. 3,364,055 issued Jan. 16, 1968 discloses a method of applying a hot melt adhesive to a carton blank. The method includes the steps of feeding carton blanks in spaced relation beneath adhesive-applying nozzles which emit a continuous stream of hot melt adhesive, and catching the emitted adhesive in a receptacle beneath the nozzle during the time that the spaced cartons are not beneath the nozzle.
U.S. Pat. No. 3,496,062 issued Feb. 17, 1970 discloses a laminate of paper and a polyethylene film sealed together with a wax composition consisting of a paraffin wax and a microcrystalline wax mixed with a copolymer of ethylene and vinyl acetate.
U.S. Pat. No. 3,522,081 issued July 28, 1970 relates to a process for preparing a coated fibrous material consisting of applying to one side of a fibrous rollable sheet material a film of a molten composition consisting of a paraffin wax, an ethylene-vinyl acetate copolymer, and alternatively an amophous resin.
U.S. Pat. No. 3,923,711 issued Dec. 2, 1975 discloses wax coating compositions prepared by subjecting a molten blend of petroleum wax and an ethylene-vinyl acetate copolymer to controlled oxidation. The controlled oxidation can take place in the presence of an oxidation inhibitor, for example, a hindered phenol.
It must be noted, however, that the wax compositions comprising a fully-refined paraffin wax, a microcrystalline wax and a polymeric hydrocarbon compound and/or in combination with a tackifier resin and phenolic anti-oxidant claimed herein are new and unappreciated by the prior art.